1. Field of the Invention
The present invention relates to an automated apparatus for inspecting columnar bodies by an eddy current method, and more particularly to an apparatus for inspecting columnar bodies with high accuracy by an eddy current method, which apparatus can be independently installed anywhere.
2. Description of Related Art
In large steel mills, all steel tubes or steel bars already finished are inspected to determine if any cracks are present, and, if any cracks are found, to measure the sizes of the cracks, thus controlling the quality of the products. Conventionally, the eddy current inspection equipment is mounted on a certain section of the production line. However, in some circumstances, for example, the space available in the steel mill is limited or the need for inspection of the above products occurs in a downstream factory, and the inspection should be carried out away from the production line. There exists a problem when inspection is being carried out by eddy current method whereby if the columnar bodies to be inspected are made of a ferromagnetic substance, a magnetic field should be imposed on the eddy current inspection equipment to enhance the precision of the inspection results. However, the magnetic field will retard the entrance of the columnar bodies into the eddy current inspection equipment or will catch the rear end portions of the columnar bodies which are leaving the eddy current inspection equipment. To resolve this problem, before feeding the columnar products into inspection equipment, it is necessary to butt adjacent end portions of consecutive columnar products, together as if they were integrally formed. Although the columnar products are disposed in a sequential manner on the production line, there should be a proper design to accommodate the inspection operation outside of the production line. Furthermore, the transportation speed of the columnar products must match the data sampling frequency so as to properly record the locations of the cracks on the columnar products. The quantity of data sampled should be designed to enhance the efficiency of processing signals and to ensure that correct analysis results are obtained. In addition, how to increase Signal to Noise Ratio of signals should be carefully considered.
It should be noted that the term "columnar bodies" indicates metal bars and metal tubes with various cross sectional shapes.
Additionally, sometimes a distorted or bent columnar body will block the passage within the inspection equipment. At this time, the operator must stop the production line to remove the bent columnar body before starting the production line again, an operation which is very inconvenient for the operator.